Merge branch 'bpf-BASE_RTT'

Lawrence Brakmo says:

====================
bpf: add support for BASE_RTT

This patch set adds the following functionality to socket_ops BPF
programs.
1) Add bpf helper function bpf_getsocketops. Currently only supports
   TCP_CONGESTION
2) Add BPF_SOCKET_OPS_BASE_RTT op to get the base RTT of the
   connection. In general, the base RTT indicates the threshold such
   that RTTs above it indicate congestion. More details in the
   relevant patches.

Consists of the following patches:

[PATCH net-next 1/5] bpf: add support for BPF_SOCK_OPS_BASE_RTT
[PATCH net-next 2/5] bpf: Adding helper function bpf_getsockops
[PATCH net-next 3/5] bpf: Add BPF_SOCKET_OPS_BASE_RTT support to
[PATCH net-next 4/5] bpf: sample BPF_SOCKET_OPS_BASE_RTT program
[PATCH net-next 5/5] bpf: create samples/bpf/tcp_bpf.readme
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 83 insertions, 3 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index 09e011f20291..ccf62f44140a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3273,7 +3273,7 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
 
 static const struct bpf_func_proto bpf_setsockopt_proto = {
 	.func		= bpf_setsockopt,
-	.gpl_only	= true,
+	.gpl_only	= false,
 	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_CTX,
 	.arg2_type	= ARG_ANYTHING,
@@ -3282,6 +3282,48 @@ static const struct bpf_func_proto bpf_setsockopt_proto = {
 	.arg5_type	= ARG_CONST_SIZE,
 };
 
+BPF_CALL_5(bpf_getsockopt, struct bpf_sock_ops_kern *, bpf_sock,
+	   int, level, int, optname, char *, optval, int, optlen)
+{
+	struct sock *sk = bpf_sock->sk;
+	int ret = 0;
+
+	if (!sk_fullsock(sk))
+		goto err_clear;
+
+#ifdef CONFIG_INET
+	if (level == SOL_TCP && sk->sk_prot->getsockopt == tcp_getsockopt) {
+		if (optname == TCP_CONGESTION) {
+			struct inet_connection_sock *icsk = inet_csk(sk);
+
+			if (!icsk->icsk_ca_ops || optlen <= 1)
+				goto err_clear;
+			strncpy(optval, icsk->icsk_ca_ops->name, optlen);
+			optval[optlen - 1] = 0;
+		} else {
+			goto err_clear;
+		}
+	} else {
+		goto err_clear;
+	}
+	return ret;
+#endif
+err_clear:
+	memset(optval, 0, optlen);
+	return -EINVAL;
+}
+
+static const struct bpf_func_proto bpf_getsockopt_proto = {
+	.func		= bpf_getsockopt,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_ANYTHING,
+	.arg4_type	= ARG_PTR_TO_UNINIT_MEM,
+	.arg5_type	= ARG_CONST_SIZE,
+};
+
 static const struct bpf_func_proto *
 bpf_base_func_proto(enum bpf_func_id func_id)
 {
@@ -3460,6 +3502,8 @@ static const struct bpf_func_proto *
 	switch (func_id) {
 	case BPF_FUNC_setsockopt:
 		return &bpf_setsockopt_proto;
+	case BPF_FUNC_getsockopt:
+		return &bpf_getsockopt_proto;
 	case BPF_FUNC_sock_map_update:
 		return &bpf_sock_map_update_proto;
 	default:
diff --git a/net/ipv4/tcp_nv.c b/net/ipv4/tcp_nv.c
index 1ff73982e28c..a978e3fa71ec 100644
--- a/net/ipv4/tcp_nv.c
+++ b/net/ipv4/tcp_nv.c
@@ -39,7 +39,7 @@
  * nv_cong_dec_mult	Decrease cwnd by X% (30%) of congestion when detected
  * nv_ssthresh_factor	On congestion set ssthresh to this * <desired cwnd> / 8
  * nv_rtt_factor	RTT averaging factor
- * nv_loss_dec_factor	Decrease cwnd by this (50%) when losses occur
+ * nv_loss_dec_factor	Decrease cwnd to this (80%) when losses occur
  * nv_dec_eval_min_calls	Wait this many RTT measurements before dec cwnd
  * nv_inc_eval_min_calls	Wait this many RTT measurements before inc cwnd
  * nv_ssthresh_eval_min_calls	Wait this many RTT measurements before stopping
@@ -61,7 +61,7 @@ static int nv_min_cwnd __read_mostly = 2;
 static int nv_cong_dec_mult __read_mostly = 30 * 128 / 100; /* = 30% */
 static int nv_ssthresh_factor __read_mostly = 8; /* = 1 */
 static int nv_rtt_factor __read_mostly = 128; /* = 1/2*old + 1/2*new */
-static int nv_loss_dec_factor __read_mostly = 512; /* => 50% */
+static int nv_loss_dec_factor __read_mostly = 819; /* => 80% */
 static int nv_cwnd_growth_rate_neg __read_mostly = 8;
 static int nv_cwnd_growth_rate_pos __read_mostly; /* 0 => fixed like Reno */
 static int nv_dec_eval_min_calls __read_mostly = 60;
@@ -101,6 +101,11 @@ struct tcpnv {
 	u32 nv_last_rtt;	/* last rtt */
 	u32 nv_min_rtt;		/* active min rtt. Used to determine slope */
 	u32 nv_min_rtt_new;	/* min rtt for future use */
+	u32 nv_base_rtt;        /* If non-zero it represents the threshold for
+				 * congestion */
+	u32 nv_lower_bound_rtt; /* Used in conjunction with nv_base_rtt. It is
+				 * set to 80% of nv_base_rtt. It helps reduce
+				 * unfairness between flows */
 	u32 nv_rtt_max_rate;	/* max rate seen during current RTT */
 	u32 nv_rtt_start_seq;	/* current RTT ends when packet arrives
 				 * acking beyond nv_rtt_start_seq */
@@ -132,9 +137,24 @@ static inline void tcpnv_reset(struct tcpnv *ca, struct sock *sk)
 static void tcpnv_init(struct sock *sk)
 {
 	struct tcpnv *ca = inet_csk_ca(sk);
+	int base_rtt;
 
 	tcpnv_reset(ca, sk);
 
+	/* See if base_rtt is available from socket_ops bpf program.
+	 * It is meant to be used in environments, such as communication
+	 * within a datacenter, where we have reasonable estimates of
+	 * RTTs
+	 */
+	base_rtt = tcp_call_bpf(sk, BPF_SOCK_OPS_BASE_RTT);
+	if (base_rtt > 0) {
+		ca->nv_base_rtt = base_rtt;
+		ca->nv_lower_bound_rtt = (base_rtt * 205) >> 8; /* 80% */
+	} else {
+		ca->nv_base_rtt = 0;
+		ca->nv_lower_bound_rtt = 0;
+	}
+
 	ca->nv_allow_cwnd_growth = 1;
 	ca->nv_min_rtt_reset_jiffies = jiffies + 2 * HZ;
 	ca->nv_min_rtt = NV_INIT_RTT;
@@ -144,6 +164,19 @@ static void tcpnv_init(struct sock *sk)
 	ca->cwnd_growth_factor = 0;
 }
 
+/* If provided, apply upper (base_rtt) and lower (lower_bound_rtt)
+ * bounds to RTT.
+ */
+inline u32 nv_get_bounded_rtt(struct tcpnv *ca, u32 val)
+{
+	if (ca->nv_lower_bound_rtt > 0 && val < ca->nv_lower_bound_rtt)
+		return ca->nv_lower_bound_rtt;
+	else if (ca->nv_base_rtt > 0 && val > ca->nv_base_rtt)
+		return ca->nv_base_rtt;
+	else
+		return val;
+}
+
 static void tcpnv_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
@@ -265,6 +298,9 @@ static void tcpnv_acked(struct sock *sk, const struct ack_sample *sample)
 	if (ca->nv_eval_call_cnt < 255)
 		ca->nv_eval_call_cnt++;
 
+	/* Apply bounds to rtt. Only used to update min_rtt */
+	avg_rtt = nv_get_bounded_rtt(ca, avg_rtt);
+
 	/* update min rtt if necessary */
 	if (avg_rtt < ca->nv_min_rtt)
 		ca->nv_min_rtt = avg_rtt;